Recyclability of four types of plastics exposed to UV irradiation in a marine environment

Plastics are the most abundant products in the world and therefore also represent the largest volume of materials found in the sea. Their resistance to degradation makes them dangerous for the marine environment. In this study, the degradation of the four main plastics (Nylon, Polyethylene (PE), Polypropylene (PP), Polyethylene terephthalate (PET)) found in the sea was observed for 6.5 months as they were exposed to UV irradiation in a marine environment. Data on changes in the physical and chemical properties of each of them were collected in order to evaluate the possibilities of material (mechanical) recycling. A thermobalance was used to look for differences in the thermal decomposition of the plastics during this time. In addition, the mechanical properties of each plastic were studied. Results showed that both thermal and mechanical properties were affected, causing a weakening of the material which became less elastic and more rigid. Furthermore, SEM and AFM images were obtained: they showed cracks, flakes and granular oxidation as well as a loss of homogeneity on the surface of the samples. These changes make mechanical recycling unfeasible, since the quality of the recycled material is insufficient to ensure a high virgin material substitution rate.